Julian Kent's kd-tree
The highlighted comment was created in this revision.
They're pretty much tied. Mine might be a little faster on systems where the data in the Kd-Tree is frequently pushed out of cache.
No, as I said above, they are mostly the same except for cache conditions.
3rd gen is the fastest of Rednaxela's trees. There's also a k-NN algorithm benchmark if you want to run some tests.
Voidious can you make a version of knn.jar with Julian Kent's tree and give instructions on how to use knn.jar on ubuntu 13.04
I've never used it, sorry.
Why not just pick Skilgannon's or Rednaxela's and go with it? The speed difference will be negligible. Unless you're locked into some insane batch job on a supercomputer upon choosing, I reckon you'll spend more time trying to evaluate them than you'll save by using one over the other.